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Retinopathy, Diabetic

Definition :
Diabetes affects your body from head to toes. This includes your eyes. The most common and most serious eye complication of diabetes is diabetic retinopathy, which may result in poor vision or even blindness.

"Retinopathy" is the medical term for damage to the tiny blood vessels (capillaries) that nourish the retina, the tissue at the back of your eye that captures light and relays information to your brain. These blood vessels are often affected by the high blood sugar levels associated with diabetes.

Nearly half of people with known diabetes have some degree of diabetic retinopathy. The longer you have diabetes, the more likely it is you'll develop diabetic retinopathy. Initially, most people with diabetic retinopathy experience only mild vision problems. But the condition can worsen and threaten your vision.

The threat of blindness is scary. But with early detection and treatment, the risk of severe vision loss from diabetic retinopathy is small. You can take steps to protect your sight if you have diabetes. These include a yearly eye examination and steps to keep your blood sugar, blood pressure and blood cholesterol under the best possible control.

Causes:
If you have diabetes, your body doesn't use sugar (glucose) properly. Sugar in your blood is vital to your health because it's a main source of energy for your body's cells. But too much sugar in your blood can cause damage throughout your body, including your kidneys, nerves, heart and eyes. Damage to the capillaries in your eyes occurs in diabetic retinopathy.

Diabetic retinopathy occurs in two types, usually affecting both eyes similarly :

  • Nonproliferative diabetic retinopathy (NPDR). This type, also called background diabetic retinopathy, is an early stage of the disease. It's the most common type of retinopathy, and symptoms are often mild or nonexistent.

    In NPDR the walls of blood vessels in the retina weaken. Tiny bulges called microaneurysms (mi-kro-AN-u-riz-umz) protrude from the walls of the small vessels in the retina. Another term for these microaneurysms is "outpouchings." The microaneurysms may begin to leak, oozing fluid and blood into the retina. As NPDR progresses, other signs of damage appear. These include swelling or beading of some of the larger retinal veins and patches of swollen nerve fibers, which are called cotton-wool spots because they look like fluffy wisps of cotton.

    Mild NPDR may not affect your ability to see clearly. Vision problems from more severe NPDR are usually the result of swelling (edema) of the central part of the retina (macula) — a condition called diabetic macular edema (DME) — or the closing of capillaries, which reduces blood flow to the macula (macular ischemia). When the macula can't function properly, your central vision decreases.

  • Proliferative diabetic retinopathy (PDR). This is the more advanced form of the disease. Retinopathy becomes proliferative when abnormal new blood vessels grow (proliferate) in the retina or the optic disc. The blood vessels also can grow into the vitreous, the clear, jelly-like substance that fills the center of your eyes.

    This abnormal growth generally follows the widespread closing of capillaries in the retina. The condition can cause vision loss affecting both your central and peripheral vision. The new blood vessels may leak blood into the vitreous, which clouds or even blocks your vision. Other complications include detachment of the retina due to scar tissue formation (traction retinal detachment) and a form of glaucoma associated with the growth of abnormal blood vessels on the iris, the colored portion of the eye surrounding the pupil (neovascular glaucoma).

Blurred vision in diabetes
Blurred vision can be brought on by rapid fluctuations in blood sugar. Prolonged periods of elevated blood sugar cause sugar and its breakdown products to accumulate in the lens. This accumulation sucks up water and makes the lens swell, resulting in nearsightedness — meaning distant objects appear blurry. The nearsightedness subsides once your blood sugar is brought under steady control.

Blurred vision can also be caused by macular swelling (edema), regardless of your blood sugar level. This is cause for greater concern because macular edema often develops in people with diabetic retinopathy. The swelling may fluctuate during the day, making your vision get better or worse. If blood vessels in your eye are hemorrhaging, you might notice spots floating in your field of vision. These small spots are often followed within a few days or weeks by larger spots or clouds, which are caused by more marked hemorrhaging.

Risk Factor :
Having diabetes puts you at risk of retinopathy, whether you have type 1 diabetes or type 2 diabetes. Your risk increases the longer you have the disease.

Other risk factors for diabetic retinopathy include :

  • Poorly controlled blood sugar levels
  • High blood pressure
  • High blood cholesterol
  • Pregnancy
  • Hispanic or African-American heritage

Neither race nor sex seems to be a factor in developing retinoblastoma.

When to seek medical advice :
A common misconception among people with diabetes is, "If I can see well, there's nothing wrong with my eyes." That's false confidence. If you have diabetes, you're at risk of diabetic retinopathy, even if you don't have any vision problems. The early detection of diabetic retinopathy is your best protection against vision loss. For this reason regular eye examinations are essential.

The National Eye Institute recommends that if you have diabetes you should receive a comprehensive dilated eye exam at least once a year. In addition, if you have diabetes and become pregnant, you should have a comprehensive dilated eye exam as soon as possible. Additional exams may be recommended throughout your pregnancy.

See your eye doctor promptly if your vision becomes blurry, spotty or hazy. If diabetic retinopathy is found, the course of treatment depends on the severity of the condition and whether your vision is currently impaired or threatened by the retinal changes.

Symptoms:
In the early, most treatable stages of diabetic retinopathy, you usually experience no visual symptoms or pain. The disease can even progress to an advanced stage without any noticeable change in your vision.

Symptoms of diabetic retinopathy may include :

  • "Spiders," "cobwebs" or tiny specks floating in your vision
  • Dark streaks or a red film that blocks vision
  • Vision loss or blurred vision
  • A dark or empty spot in the center of your vision
  • Poor night vision
  • Difficulty adjusting from bright light to dim light

Diagnosis:
Your eye doctor will likely diagnose diabetic retinopathy, either nonproliferative or proliferative, if an eye examination reveals any of the following :

  • Leaking blood vessels
  • Retinal hemorrhage
  • Swollen retina
  • Fatty deposits (exudates) in the retina
  • Areas of nerve fiber damage (cotton-wool spots)
  • Changes in blood vessels, such as closures, beading or loops
  • Microaneurysms
  • Formation of new blood vessels (neovascularization)
  • Vitreous hemorrhage
  • Scar tissue formation with retinal detachment

As part of an eye examination, your doctor may include a diagnostic procedure called fluorescein angiography to identify leaking blood vessels.

In fluorescein angiography, your doctor injects a dye into a vein in your arm. The dye circulates through your eyes, making the blood vessels in your retina easy to identify. Your doctor can pinpoint areas where normal blood vessels have become closed or have broken down and are leaking fluid. A camera with special filters takes flash pictures every few seconds for several minutes, providing your doctor with useful images.

Your doctor also may request an optical coherence tomography (OCT) examination. This noninvasive imaging scan provides high resolution images of the retina that show, for example, the thickness of the retina and whether fluid has leaked into retinal tissue. OCT exams can be useful both as a diagnostic tool and as a way of monitoring treatment effectiveness.

Complications :
The abnormal growth of new blood vessels in proliferative diabetic retinopathy doesn't resupply the retina with a normal blood flow. Instead, these abnormal vessels may produce other complications :

  • Vitreous hemorrhage. The new blood vessels may bleed (hemorrhage) into the vitreous. If the amount of bleeding is small, you might see only a few dark spots or floaters. In more severe cases, blood can completely fill the vitreous cavity and block all of your vision. Vitreous hemorrhage by itself usually doesn't cause permanent vision loss. The blood often clears from the eye initially — within a few weeks or months — and your vision may return to its previous clarity, unless your retina is damaged.
  • Traction retinal detachment. The new blood vessels, if not stopped early in their development, are accompanied by the growth of scar tissue. The scar tissue can shrink and pull the retina away from the back wall of the eye. This causes blank or blurred areas in your field of vision, even complete loss of vision in severe cases.
  • Neovascular glaucoma. The proliferation of blood vessels in the retina and vitreous may be accompanied by the growth of abnormal new blood vessels on the iris. This can interfere with the normal flow of fluid out of your eye and cause pressure in your eye to build up. The result is neovascular glaucoma, a serious complication of diabetic retinopathy that can cause damage to your optic nerve and even destroy your eye.

Treatment:
The abnormal growth of new blood vessels in proliferative diabetic retinopathy doesn't resupply the retina with a normal blood flow. Instead, these abnormal vessels may produce other complications :

  • Vitreous hemorrhage. The new blood vessels may bleed (hemorrhage) into the vitreous. If the amount of bleeding is small, you might see only a few dark spots or floaters. In more severe cases, blood can completely fill the vitreous cavity and block all of your vision. Vitreous hemorrhage by itself usually doesn't cause permanent vision loss. The blood often clears from the eye initially — within a few weeks or months — and your vision may return to its previous clarity, unless your retina is damaged.
  • Traction retinal detachment. The new blood vessels, if not stopped early in their development, are accompanied by the growth of scar tissue. The scar tissue can shrink and pull the retina away from the back wall of the eye. This causes blank or blurred areas in your field of vision, even complete loss of vision in severe cases.
  • Neovascular glaucoma. The proliferation of blood vessels in the retina and vitreous may be accompanied by the growth of abnormal new blood vessels on the iris. This can interfere with the normal flow of fluid out of your eye and cause pressure in your eye to build up. The result is neovascular glaucoma, a serious complication of diabetic retinopathy that can cause damage to your optic nerve and even destroy your eye.
 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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